This proposal details a 5 year training program to develop the skills necessary to pursue independent research in basic science. The principal investigator, a board-certified Pediatrician completing the third year of fellowship training in Neonatology, is currently applying for an elective year of fellowship training to lay as strong a foundation as possible for a successful career in academic medicine. This training program centers upon studies of altered ovine coronary artery physiology following antenatal corticosteroid exposure. The global hypothesis is that dexamethasone-induced downregulation of coronary artery cyclooxygenase (COX)-depenendent prostaglandin and reactive oxygen species (ROS) production is an important aspect of fetal programming, resulting in heightened coronary artery tone. Such alterations in coronary artery reactivity could provide a mechanistic explaination for the observed associations between an adverse intrauterine environment, low birth weight and subsequent coronary artery disease. Dr. Jeffrey Segar will mentor the Pi's training with Dr. Fred Lamb acting as co-sponsor. They are well established investigators in ovine cardiovascular physiology, and their mutual interest in the study of coronary artery dysfunction 'fosters an intellectually stimulating collaborative environment that has already propelled others into successful research careers. Dr. Roghair's preliminary data demonstrating steroid-induced alterations in COX-mediated vascular reactivty in association with deceased basal ROS production has led to the evolution of the following specific aims: 1) define the role of prostaglandins in the fetal programming of coronary artery dysfunction;2) test the hypothesis that early gestation dexamethasone exposure alters arachidonic acid-induced reactive oxygen species production;and 3) determine whether the observed alterations in conduit coronary artery reactivity are seen in physiologically-relevant resistance coronary arterioles.